Filament clamp and tensile tester



FILAMENT CLAMP AND TENSILE TESTER May 13, 1958 United States Patent2,834,204 FILAMENT CLAMP AND TENSILE TESTER Richard H. Braunlich, WestChester, Pa., assignor to American Viscose Corporation, Philadelphia,Pa., a corporation of Delaware Application March 30, 1955, Serial No.497,899

4 Claims. (CI. 73-95) This invention relates to tensile testingapparatus, and more particularly to a device for obtaining elongationand tensile strength measurements on filamentary material such as threadand yarn.

In using conventional apparatus for obtaining readings of elongation andtensile strength of textile filaments, difficulty has been encounteredin providing adequate means for securing the filament or tow in such away that rupture does not occur at the point of attachment due to thesharp radii inherent in tying a knot. When a pressure type clamp isused, it is almost impossible to obtain equal clamping pressure on allthe individual fibers or filaments and to avoid damaging or crushing thefilaments in contact with the clamp. These disadvantages have introducedboth large and small errors in the measurement of elongation and instress-strain data.

The present invention avoids these disadvantages by securely anchoringthe ends of the test sample in a medium comprising magnetizable metallicparticles suspended in a fluid such as oil. These magnetic oil-metalmixtures are well known and form no part of the present invention. Atypical mixture is described in Lucas Patent No. 2,148,782 but themercury specified therein is not essential to the mixture for use withtextile strands and filaments. When the tow or yarn is immersed in themagnetizable mixture, it is securely frozen or clamped so that there isno possibility of rupture due to knotting. With the use of asurface-active agent, the magnetizable fluid Will penetrate the tow sothat each filament will be securely held in place without relativemovement of the filaments occurring within the bundle. Thesurface-active agent should be chosen to provide satisfactory wetting ofthe particular filaments with the type of fluid being used.

A primary object therefore of the present invention is to provide anovel and improved clamp for yarn and tow bundles.

A further object of the invention is to provide a novel and improvedclamp for yarn and tow bundles comprising a receptacle having amagnetizable fluid therein, and a magnetic field surrounding thereceptacle which can be selectively energized to freeze the yarn samplein the receptacle.

A further object of the invention is to provide a novel and improvedstress-strain testing apparatus in which highly accurate results can beobtained.

Further objects will be apparent from the specification and drawings inwhich:

Figure 1 is a side view showing a yarn tow stress-strain test apparatusembodying the present invention; and

Figure 2 is a vertical sectional view on an enlarged scale of one of theyarn clamps of the present invention.

The invention comprises essentially the provision of a pair ofreceptacles containing a magnetizable oil-metal mixture with eachreceptacle being surrounded by a coil which freezes the mixture when thecoils are electrically energized. Each receptacle is mounted onsupporting 2,834,204 Patented May 13, 19 58 trunnions in a saddle on atensile testing machine so that both of the receptacles are horizontallypositioned during the test. Under these conditions, the fluid is alwaysfrozen so that it will not run out of the receptacle; but when the coilfor each receptacle is deenergized, the receptacles are always in aVertical position with the fluid contained therein in a fluid state.

Referring now more particularly to the drawings, a stress-strain testingapparatus embodying the present invention comprises a central standard 5to which a horizontal beam 6 is pivoted at 7. A suitable counterbalance8 for the beam is adjustable on a rod 9 to balance the weight of thebeam. The beam may be pivoted on standard 5 by means of a threaded shaft10 pivoted to the outer end of the'beam at 11 and extending downwardlythrough a nut 12 which is turned by means of a reversible motor 13 andgear reduction unit 14. The beam 6 carries a track 15 on which acarriage 16 is movable by means of rollers 17, 17. The track 15 extendsbeyond the beam to the opposite side of pivot 7 and is graduated at .18to enable clamped to the track at a desired predetermined position.Bracket 19 has a saddle 20 in which the yarn clamp as sembly 21 ispivoted. A bracket 22 is connected to carriage 16 and likewise carries ayarn clamp assembly 23 pivoted thereto.

Each of the clamp assemblies 21 and 23 is identical and is shown ingreater detail in Figure 2; therefore, only one will be described. Areceptacle or cup 24 is enclosed in a nonconductive housing 25 in whichthere is embedded a coil 26 which can be electrically energized when acircuit is closed through leads 27 and 28. The housing 25 and thereceptacle are supported on trunnions 29, 29 as described above.

The yarn or tow sample 8 to be tested is submerged in A the magnetizablefluid F by means of a weight W tied to one end of the sample or it maybe pushed into the fluid by means of a separate instrument. When theproper length of sample has been submerged, the fluid is solidified orfrozen by energizing the coil 26. The same procedure is followed forattaching the other end of the test sample S to the clamp 23. With bothends of the sample securely clamped, the carriage 16 and the clamp 19are secured at the proper zero positions on track 15 so that the clamps21 and 23 are pivoted through arcs of with the sample stretchedtherebetween. The motor 13 is then started to pull shaft 10 downwardlyin accordance with conventional test procedure. The weight of carriage16 is therefore gradually applied to the test sample and the downwardtravel of the carriage on track 15 can be indicated or recorded by meansof a suitable marker or stylus 30.

Suitable calibration between the angle through which beam 6 is pivotedor the time that motor 13 runs permits calculation of the stress appliedto the sample and thus a stress-strain diagram can be plotted. If theultimate strength is desired, motor 13 continues to run until the sampleruptures. The motor is reversed to return the beam to its initial zeroposition whereupon the clamps 21 and 23 will pivot to their verticalpositions as shown in Figure 1, and the fluid is desolidified bybreaking the circuit tothe coils so that the tested sample or brokenends thereof are readily removed.

The present invention provides an improved apparatus for clampingtextile yarn test samples and other objects in which the ultimatestrength of the sample or the stress applied is less than the forcerequired 'to pull the sample out of the clamp.

Having thus described my invention, I claim:

1. A stress-strain testing apparatus for filamentary material and thelike comprising a bracket, a receptacle pivotally mounted in saidbracket, a magnetizable fluid the slidable bracket 19 to be t 3miXturein said receptacle, a second receptacle, a bracket in which saidsecond receptacle is pivotally mounted, a magnetizable fluid mixture insaid second receptacle, means for magnetizing the fluid mixture in eachof said receptacles to solidify the fluid mixture, and means for movingsaid receptacles away from each other when the fluids are solidified.

2. In stress-strain testing apparatus having a pivoting beam, means forcontrollably pivoting said beam, a carriage movable on said beam, andmeans for indicating the relative movements of the beam and thecarriage, the improvement which comprises a pivotally mountedreceptacle. on the beam, a pivotally mounted receptacle on the carriage,'a magnetizable fluid mixture in said receptacles, a coil surroundingeach receptacle, and an electrical circuit connected with each coil,said coil and circuit serving to magnetize the fluid mixture to solidifythe fluid mixture.

3. Apparatus in accordance with claim 2 in which the receptacles "aremounted in trunnions.

4. A stress-strain testing apparatus for filamentary material and thelike comprising a first pivotally mounted receptacle, a magnetizablefluid mixture in said receptacle, a second pivotally mounted receptacle,a magnetizable fluid mixture in said second receptacle, a coilsurrounding each receptacle, an electrical circuit connected with eachcoil, said coil and circuit serving to magnetize the fluid mixture tosolidify the fluid mixture, and means for moving said receptacles awayfrom each other when the fluids are solidified.

Refereuces Cited in the flle'of this patent UNITED STATES PATENTS

